What climate science doesn’t tell us

In an earlier post I criticised Australia21 for the lofty certainties of its Beyond Denial publication, and sent a copy to the organisation. I should say again that I have supported other publications of this think-tank, notably the one on decriminalising illegal drugs, where I think it has the right arguments and the right proposals. In the climate domain, however, it seems to me an uncritical supporter of the orthodoxy.

In due course I received a reply which rejected my criticisms, root and branch. The writer dismissed what I had said as not ‘seriously challenging the evidence that catastrophic climate change is a real threat that we cannot afford to ignore except at our children’s peril.’ Was it worth responding to that? I decided that it would be good for me to consider how one would deal with such a claim, and finally wrote a response. The core of it follows.

The Beyond Denial booklet relied, presumably, on the IPCC reports, especially the last one in 2007, so the right way to go is to take each of the IPCC core claims and assess them against the evidence. There are five them, set in bold, with my comments following.

1. The world has warmed in the 20th century and especially since 1950.

The world has probably warmed about 0.7C since 1950, according to HadCRUT3 data. Prior to 1950 the amount of the Earth’s surface for which data are available falls away but it does seem likely that temperatures rose 1920-45, were flat 1946-1976, warmed 1977-97 and for the last 16 years have been flat.

2. That warming is unprecedented.

Given our necessary uncertainty about the level of warming in the 20th century it is hard indeed to show whether or not it is unprecedented. In any case all our knowledge about past warming comes through proxies for temperature in tree rings, sediments, oxygen isotopes, stalactites and the like, and they come with their own uncertainties and errors. Even so, there is evidence that that there could have been as much as 3 degrees of warming between 8000 and 8200 years ago. Of course we do have direct historic evidence that the earth, or parts of it, has been warmer and cooler at other times, but we can’t say much more than that. (See http://mclean.ch/climate/Ice_cores.htm.)

3. Much if not most of that warming is directly due to human activity in burning fossil and other fuels, clearing forests, making cement, and the like.

I am unaware of any scientific paper that has been able to measure the human influence on global warming, and the IPCC’s confidence rests on the output of computer models. AR4’s WG1, in Table 2:11, shows how little we understand even radiative heat transfer, and that is only a small sub-set of all climate forces. WG1’s Chapter 8 contains more than a dozen statements about the failings of climate models. We do not yet have any real measure of the nature, extent and causes of natural variability, and the ‘signal’ of human influence would have to be distinguished within it. No one has yet done this.

4. We are on a trajectory that leads inevitably to large increases in temperature, which is likely to disrupt human life as we have known it (there are many ways of expressing this anxiety, but I think this is a fair one).

Mainstream physics tells us that a doubling of carbon dioxide in the atmosphere would lead, all things being equal, to an increase in temperature of around 1.1 degrees C. This well within the capacity of human and social life as we known it. Since most of that increase (if it is thought to have begun in 1780, or at the beginning of the industrial revolution) has already taken place, and because the increase is logarithmic, the rest of the warming should take place quite slowly. The IPCC introduces ‘climate sensitivity’ to amplify the effects, but there is no agreed figure for the proposed positive feedback from water vapour and clouds, which might prove to be low or even negative. Certainly there is no figure established by evidence and strong argument.

All of this, in any case, is based on theoretical and measured physics in laboratory conditions. How any of it actually plays out in the real world is not known — for example, more heat means more evaporation and more convection, and the net result might simply be that gains and losses in heat just occur more quickly. Further, on balance, extra warming is likely to be on the whole beneficial for humanity. A degree of cooling would certainly not be. Nor is there any evidence that there exists a ‘tipping point’ after which warming proceeds in some kind of out-of-control mode. This, like so much of what passes for ‘climate science’ in the mainstream media, is simply conjecture. And there has been no discernible warming for the past 16 years, though CO2 has been increasing. All in all, the trajectory is not obvious.

5. We must therefore do everything we can to prevent further increases in warming, through a global effort to ‘combat climate change’ through ‘weaning ourselves off fossil fuels’ (these phrases do not come from AR4, but are commonly used by our leaders).

This is not a scientific statement anyway, though it is central to the justification of what is done in measures like the carbon tax, proposed taxes on flights, and the like. In any case, no global agreement has happened, despite twenty years of pressure from NGOs and the UN. It doesn’t seem likely to happen in the next ten years or so, and the increased emissions from China and India dwarf in a month anything Australia could do in two years. Without clear and credible evidence that CO2 is causing significant and dangerous warming I cannot see the point in reducing the burning of fossil fuels, moving into wind turbines, and the rest of it. Current scientific understanding provides no justification for any action.

It puzzles me that people are so certain about ‘catastrophic’ and ‘anthropogenic’ global warming when we still can’t even measure the key variables. But belief is a powerful thing, and as I have said before, this belief makes believers feel that today is the most important time of all, and that they are the potential saviours of mankind.

I’ve had no response yet.

Share this:

Join the discussion 3 Comments

Good summary. The most telling point is that the world has not warmed for 16 years, despite a large increase in emissions over this period. This destroys the hypothesis that CO2 emissions lead to temperature rises.